Can it rain oily compounds in the Gulf of Mexico? Yes! Chris Landau geologist & meteorologist

Can it rain oily compounds in the Gulf of Mexico? Yes! Chris Landau geologist & meteorologist

Do not let your kids eat the hail or drink the rainwater. It is likely to contain some benzene and cyclohexane. Can it rain oily compounds? The short answer is it certainly can. It is also not complex to work out which chemical compounds will be coming down in our rainwater. It is those with a similar boiling point and freezing point to water. It is those that are not too heavy, that are similar to that of air at 1.2 kg per cubic meter. They should be able to rise easily to upper atmospheric levels.

Let us start with water. On earth at everyday working temperatures matter has 3 phases. They are solid, liquid and gas. We know these phases by other names called ice, water and steam.

Water is ICE or a SOLID at 32 degrees F or below that temperature. It turns to WATER or a LIQUID at temperatures slightly above 32 degrees C. It starts evaporating as soon as it is liquid and starts changing to steam or vapor until at our atmospheric pressures, at sea level, it is all STEAM or WATER VAPOR or GAS at 212 degrees F.

In the case of benzene and cyclohexane, these chemical compounds found in oil, change from a solid (ice) at 42 and 44 degrees F, and start evaporating rapidly until at 176 and 177 degrees F they are all vapor or gas.

I have read where the first few minutes of a rain are the most polluted.

That is because the atmosphere contains airborne particles of all kinds and as the first rain drops fall they connect with and drag to the surface those particles.

After a few minutes the air is pretty much cleaned out and the rain is pure.

However, given that the massive oil slick has somewhat evaporated in a massive way, it could be that the clouds themselves are polluted and all the rain that falls from the skies above the slick are dangerous from start to finish?

5. I expect that first moments are worst would certainly be true with particulates

However with vapors I would expect the pollutedness of the rainwater to be distributed along the condensation points of the contaminates. Is acid rain more or less acidic as the rain falls? I don't know, but expect it would be relatively evenly distributed.

Having been one of those fools who doesn't always know to get in out of the rain, and having been merrily drenched, maybe too many times, I do know that when the rain first commences - in a thunderstorm especially-- the downdraft can be quite a force pushing a large part of the atmosphere down to the ground.

IIRC, the onset of an acid rain is measurably more acidic, which was probably read about in the same paper that mentioned the extra pollution in the first few minutes a rain event.

I did a good deal of research on acid rain awhile back. After all, one of my chief occupations is cloud watching.....

He's claiming that about cyclohexane and benzene, so I have to assume he'd say the same about water.

It's a false claim, of course. Even at freezing and below, water still has a vapor pressure--a quantity of water that stays in the air, at equilibrium with the frozen water. That's a standard thing taught in first year college chemistry. Or high school chemistry. Q.v. "triple point" or "vapor pressure." The same is true for benzene and cyclohexane.

It's odd that a meteorologist wouldn't know that he actually routinely saw air moisture content when the temps were before freezing. That freezer burn was a great mystery to him isn't surprising.

Having been a foolish chemistry geek in high school, I actually had benzene in a polyethylene jar. It was evaporating, so I chucked it in the freezer. It froze. It still escaped into the air, since the partial pressure of benzene in freezer << vapor pressure. You could smell it when you opened the freezer and I was annoyed when I checked and found my benzene had all sublimated. And, yes, this was before the carcinogenic effects of benzene were widely known. I kept the cyclohexane in a glass jar, so it didn't need to be frozen.

The question is whether the concentration of cyclohexane or benzene up there at 32k feet is going to be less than, the same as, or greater than the vapor pressure. Otherwise there'll be very slight amounts in the water--some certainly would dissolve, but not even much of what's in the air--and would survive the trip down.

On the other hand, anybody who's actually handled benzene and cyclohexane would be loath to describe them as "oily."

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